WASHINGTON — The Environmental Protection Agency’s staff has concluded that the government needs to tighten smog rules by somewhere between 7 and 20 percent.

In its final recommendation in a 597-page report, the agency staff agrees with EPA’s outside scientific advisers that the 6-year-old standard for how much smog is allowed needs to be stricter, saying it will save a significant number of lives and cut hospital visits. An earlier version of the report came to a similar conclusion.

Industry representatives criticized the recommendation as way too costly, while environmental activists hailed it as a public health measure.

Since 2008, the standard has allowed up to 75 parts of ozone per billion parts of air. The staff report recommends between 60 and 70 parts per billion. The report says it will provide more health protection for higher-risk populations, including the elderly, very young, outdoor workers and people with asthma and lung disease. And it estimated that there are tens of millions, if not more than 100 million people, in that at-risk category.

When the agency tried to make a similar rule a few years ago, it estimated it would cost up to $90 billion a year, making it one of the most expensive environmental regulations ever proposed. After industry and Republicans in Congress criticized it, President Obama withdrew it in 2011.

Ross Eisenberg, a vice president at the National Association of Manufacturers, said Friday the rule that staff recommends would cost up to $270 billion a year.